1. Field of the Invention
The present invention relates to a tiltable headrest for a vehicle seat, and more particularly, the present invention relates to a tiltable headrest for a vehicle seat which has a hinge part for allowing a support bar to be rotated within a predetermined angle relative to a body support frame supporting a headrest body, the hinge part having a pair of annular leaf springs intervened between the body support frame and a head portion of a rivet serving as a hinge shaft such that they are brought into back-to-back contact with each other and a pair of flat washers fitted around the hinge shaft at both sides of a flat end portion of the support bar, respectively.
2. Description of the Related Art
Generally, a headrest provided at an upper end of a seat back in a vehicle or an aircraft is used in a state that both ends of a support bar 20, which are embedded into a headrest body 10, are fitted into a pair of guide holes formed in the seat back, respectively, as shown in FIG. 1. However, in this headrest structure, because the headrest body 10 is securely fixed to the support bar 20, it is impossible for a driver or passenger to adjust the angle of a headrest.
To solve this problem, a technique for allowing a headrest to be tilted is disclosed in Korean Utility Model Publication Gazette No. 93-7220. According to the technique, in a headrest provided at an upper end of a seat back, a lower end of a support member is embedded into the seat back, and an angle adjustor having a sector-shaped configuration is integrally molded to an upper end of the support member. A center hole is formed at a center portion of the sector-shaped angle adjustor, and a guide groove is formed adjacent to an edge portion of the sector-shaped angle adjustor such that it circumferentially extends. A plurality of headrest support fixing holes are formed in the guide groove such that they are circumferentially spaced apart one from another. A space into which the sector-shaped angle adjustor is received is defined in a lower end of a headrest body. One end of a headrest support around which a coil spring is wound, is secured into a wall portion of the headrest body, which defines the space for receiving the sector-shaped angle adjustor. A long shaft portion of the headrest support is passed through the center hole, and a short shaft portion of the headrest support is passed through one of the plurality of headrest support fixing holes.
However, the tiltable headrest constructed as mentioned above encounters a problem in that the sector-shaped angle adjustor must be integrally molded to the upper end of the support. Further, since the headrest support is assembled to the angle adjustor such that the short shaft portion thereof is passed through one of the plurality of headrest support fixing holes, the assembling operation cannot be performed in an easy manner. In addition, because the space for receiving the angle adjustor must be defined in the headrest body, the headrest body must be separately formed having this space.
In view of these problems, a tiltable headrest as shown in FIG. 2 is disclosed in the art. In the tiltable headrest as shown in FIG. 2, a hinge part 30 is provided at a lower end of a body support frame 11 which supports a headrest body 10 as shown in FIG. 1. An upper end of a support bar 20 is rotatably coupled to the hinge part 30 by a hinge shaft 33. The hinge part 30 has a first limiter 31 which can be brought into contact with a lower portion of the support bar 20 and a second limiter 32 which can be brought into contact with an upper portion of the support bar 20. An auxiliary guide arrangement 40 which surrounds the hinge part 30, includes first and second guide members 43 and 44 which cooperate with each other to define a hinge part receiving space 42 therebetween. The first guide member 43 is formed with a projection 45, and the second guide member 44 is formed with a groove 46 into which the projection 45 is engaged. Between lower ends of the first and second guide members 43 and 44, there is defined a support bar guide groove 41 which allows the support bar 20 to be rotated therein within a predetermined angle.
Referring to FIG. 3, there is shown a schematic perspective view illustrating the tiltable headrest of FIG. 2, which is in an assembled state. In FIG. 3, the hinge part 30 shown in FIG. 2 is received into the hinge part receiving space 42 which is defined by the first and second guide members 43 and 44 of the auxiliary guide arrangement 40 in a state that the support bar 20 and the body support frame 11 are rotatably coupled to the hinge part 30, and the projection 45 is engaged into the groove 46. At this time, because the support bar 20 is fixedly secured to the seat back, the body support frame 11 is actually rotated, whereby the angle of a headrest body 10 can be adjusted.
Referring to FIG. 4, there is shown a side view illustrating an independent appearance of the hinge part of FIG. 2. As described above, the body support frame 11 and the support bar 20 are rotatably coupled to each other by the hinge shaft 33 of the hinge part 30. The hinge part 30 has the first and second limiters 31 and 32, and the support bar 20 is rotatably coupled to the hinge part 30 via the hinge shaft 33. At this time, since the upper end of the support bar 20 is rotatably coupled to the hinge part 30 by the hinge shaft 33 while a wear-resistant packing 34 is intervened therebetween, once the support bar 20 is rotated relative to the body support frame 11 to adjust the angle of the headrest body 10, the adjusted angle of the headrest body 10 is maintained as it is, and accordingly, there is no need for separate angle adjusting means. At this time, even though the body support frame 11 is actually rotated about the hinge part 30 due to the fact that the support bar 20 is fixedly secured to the seat back, it was stated, in view of convenience of illustration and explanation, that the support bar 20 is rotated about the hinge part 30.
FIG. 5 is a side view illustrating the hinge part 30 of FIG. 4, which is surrounded by the auxiliary guide arrangement 40. As described above, the body support frame 11 and the support bar 20 are rotatably coupled to each other by the hinge shaft 33 at the hinge part 30. The hinge part 30 has the first and second limiters 31 and 32 which function to delimit a rotating angle of the support bar 20. For doing this, it is preferred that the upper end of the support bar 20 is formed as a flat end portion 23 and first and second stepped portions 21 and 22 are formed on lower ends of both flat side surfaces of the flat end portion 23, respectively, which correspond to the first and second limiters 31 and 32. Of course, the packing 34 is provided at the upper end of the support bar 20, which is formed as the flat end portion 23, such that the support bar 20 is coupled to the hinge part 30 by the hinge shaft 33 while being biased by the packing 34. At this time, although the support bar 20 is illustrated in FIG. 5 as being rotated, it is to be readily understood that since the support bar 20 is fixedly secured to the seat back, the body support frame 11 is actually rotated about the hinge part 30 to adjust the angle of the headrest body 10. Accordingly, due to the fact that the hinge part 30 is received into the hinge part receiving space 42 and the support bar guide groove 41 is defined at a lower portion of the auxiliary guide arrangement 40, which corresponds to the support bar 20, for example, if the body support frame 11 is rotated in a clockwise direction while the support bar 20 is held in a position depicted by the one-dot chain line in FIG. 5, a positional relationship between the support bar 20 and the body support frame 11 can be depicted as represented by the solid line in FIG. 5. When explaining the support bar 20 as being rotated, in view of illustration convenience, since the support bar 20 is rotatably coupled to the hinge part 30 by the hinge shaft 33 while the packing 34 is intervened between the support bar 20 and the hinge part 30 to bias them toward each other, the angle of the headrest body 10 can be adjusted with no provision of separate angle adjusting means. In other words, by applying force to the headrest body 10 while overcoming the biasing force of the packing 34, it is possible to adjust an angle of the headrest body 10. Moreover, when the support bar 20 reaches a limit of the predetermined angle after being rotated along the support bar guide groove 41, it is prevented from being overly rotated, by the fact that the first limiter 31 or the second limiter 32 is engaged with the first stepped portion 21 or the second stepped portion 22, respectively. In addition, since the support bar 20 can be freely rotated along the support bar guide groove 41 while its contact with cushioning material of the headrest body 10 is prevented by the auxiliary guide arrangement 40, the headrest body 10 is protected from being damaged even when the angle adjustment operation is repeatedly performed.
Referring to FIG. 6, there is shown a cross-sectional view of the hinge part 30 of FIG. 4. As described above, the body support frame 11 and the flat end portion 23 of the support bar 20 are rotatably coupled to each other by the hinge shaft 33. An annular leaf spring serving as the packing 34 is intervened between the body support frame 11 and a head portion 33-1 of a rivet serving as the hinge shaft 33, and a nylon washer 35 serving as another packing is intervened between the body support frame 11 and the flat end portion 23 of the support bar 20. By this, as the annular leaf spring 34 is depressed by the head portion 33-1 of the rivet 33, it biases the body support frame 11 toward the flat end portion 23 of the support bar 20. Accordingly, frictional force which can be generated at the nylon washer 35 intervened between the body support frame 11 and the flat end portion 23 of the support bar 20, is increased, thereby to maintain an inclination angle of the body support frame 11 as it is.
However, the tiltable headrest of the related art, constructed as mentioned above, suffers from defects in that if the angle adjusting operation for the body support frame 11 is performed up to several hundred times, for example, about 400-500 repeat count, as the nylon washer 35 is worn out, the frictional force is decreased, and as the annular leaf spring 34 and the body support frame 11 are worn out at their contact region, the frictional force is further decreased, whereby it is difficult to maintain an angle of the headrest body 10, which is established by the angle adjusting operation, as it is.